These proceedings represent the work of contributors to the 18th European Conference on Cyber Warfare and Security (ECCWS 2019), hosted by University of Coimbra, Portugal on 4 - 5 July 2019. The Conference Chair is Tiago Cruz and the Programme Chair is Paulo Simoes from University of Coimbra. ECCWS is a well-established event on the academic research calendar and now in its 18th year, the key aim remains the opportunity for participants to share ideas and meet the people who hold them. The scope of papers will ensure an interesting two days. The subjects covered illustrate the wide range of topics that fall into this important and ever-growing area of research. The opening keynote presentation is given by Dr. Leandros A. Maglaras, from the National Cyber Security Authority of Greece on the topic of Protection of Critical National Infrastructures. The second day of the conference will open with an address by Nuno Medeiros, EDP Distribuição, Lisbon, Portugal, who will talk about Cyber Security Challenges for a Critical Infrastructure Operator. With an initial submission of 157 abstracts, after the double blind, peer review process there are 74 Academic research papers, 12 PhD research papers, 8 Masters Research papers, 4 non-academic papers and 4 work-in-progress papers published in these Conference Proceedings. These papers represent research from Australia, Austria, Bahrain, Brazil, Bulgaria, Canada, Czech Republic, Estonia, Finland, France, Germany, Greece, Indonesia, Ireland, Israel, Latvia, Lithuania, Malaysia, Mozambique, Netherlands, Norway, Portugal, Romania, Russia, South Africa, South Korea, Sweden, Taiwan, United Kingdom and the United States of America. We hope you enjoy the conference.